Shielding for high frequency apparatus



Aug. 30, 1932. H o E soN 1,875,132

SHIELDING FOR HIGH FREQUENCY APPARATUS Filed Dec. 21, 1928 lvwnto HAROLD 0. PETERSON 8351 HS &um 13 Patented Aug. 30, 1932 UNITED STATES PATENT OFFICE HAROLD O. PETERSON, OF RIVERHEAD, NEW YORK, ASSIGNOR TO RADIO CORPORATION OF AMERICA, A CORPORATION OF DELAWARE SHIELDING FOR HIGH FREQUENCY APPARATUS Application filed December 21. 1928. Serial No. 327,562.

This invention relates to shielding for high frequency apparatus, and more particularly to the shielding of short wave radio equipment.

When Very high frequencies are dealt with considerable precaution must be taken to carefully shield the apparatus and circuits employed. Not only must the individual resonant circuits be carefully shielded, but the leads interconnecting these circuits also must be shielded. Because of the high reactance which even a straight piece of conductor ofters to Very high frequency energy, and to reduce natural capacitive coupling, it is desirable to keep the leads as short as possible. Tubes especially designed for high 'frequency work, as for example the screen grid tube, are ordinarily arranged with the control electrode terminal at one end of the tube, and the anode terminal at the other end of the tube. Advantage may be taken of this to convey energy from one stage to another, when intercoupled by a tube, or to couple a shielded resonant input circuit and a shielded resonant output circuit with the tube, by perinitting the tube itself to pass through a partition, and then coupling the input circuit in one of the conpartments to the control electrode terminal of the tube projectng within that compartment, and the output crcuit to the anode terminal within its compartment.

An arrangement with horizontal partitions requires the various stages of the receiver to be located one above another, in-

` stead of along side of one another, as is more customarily the case, while sloping partitions are wasteful of space. According to my invention I use the tube as a coupling means, and I attain or even improve on the compactness of the usual arrangement having imperforate Vertical partitions by arranging the tube so that it passes through a vertical partition. The tube is preferably kept in a nearly upright position, but with suflicient slant to bring the control electrode terminal within one compartment and the anode terminal within the adjacent compartment.

It has been found desirable, when working with the high frequencies in question, to shield the tube, as well as the leads and resonant circuits. In fact, even when employing a screen grid tube it is well to augment the shielding action of the screen grid by a shield completely surrounding the tube. In order to provide for this I employ a vertical conductive partition having a cylindrical conductive shield extending therethrough at a slant, so that a tube positioned within the shield, while shielded thereby, has its opposite ends accessible on opposite sides of the partition. Of course, the shielding, including the cylindrical shield, is ordinarily grounded, and, if a screen grid tube is employed, the screen grid is connected directly to the shield, at least with respect to radio frequeney energy.

The invention is described more in detail in the following specification, which is accornpanied by a drawing in which Figure 1 is a section through an amplifier, showing the arrangement of the tubes, while Figure 2 is a wiring diagram of the arrangement shown in Figure 1.

Referring to Figure 1, it will be seen that there is a conductive shielding container 2, which is divided into a pluralityof compartments by vertical conductive partit-ions, such as 4 and 6. The electron emission tubes 8 and 10 are provided with control electrode terminals 12 and 14 at one end, and anode terminals 16 and 18 at the other end. The tubes are passed through the partitions 4 and 6, so that the terminals 12 and 16, and 14 and 18, are on opposite sides of the partitions. The tubes should preferably be kept as nearly uprght as possible in order to conserve space, and also in order to cause minimum bending Stress on the tube cathode.

The tubes 8 and 10 are surrounded by cylindrical conductive shields 20 and 22. These pass through the partitions 4 and 6, as shown, and are preferably afixed integrally thereto by solderin around the surface of the cylindrcal shield.

The invention is applicable to various forms of apparatus, but Fgures 1 and 2 exemplify a. simple two stage amplifier, to which energy is fed by a lead 24, and coupled through a coil 26 to a resonant input cireuit 28. An astatic shield 30 may be provided between the primary and secondary coils in order to prevent capacitve coupling therebetween. One side of the resonant input circuit 28 is coupled by the lead 32 to the control electrode terminal 12, while the other side is grounded to the shield with respect to ,radio requencies, preferably through a blocking condenser 34, in order to make possible the.

application of direct bias potential to the control electrode ofthetube, as is better indicated in Figure 2. Theoutput energy is taken fron the anode terminal 16 to one side of the resonant out-put"circuit 36, 'the other side of which is connected. to the shield through a blocking condenser 38. Fhe out put circuit acts also as an inputcircuit for tube, and a control electrode terminal at the other end of the tube, said tube being placed at an angle relative to-the vertical and positioned within said cylindrical shield so that the control electrode terminal is in one compartment while the anode terminal is in the ad acent compartment, an input circuit situated in the first compartment, an output cir cuit Situated in the second compartment,

means coupling the input circuit to the con trolelectrode terminal, and `means coupling the output circuit to the' anode terminal.

' HAROLD Q PETERsON.

the nextiamplifier stage, and for this purpose one side of the resonant circuit 36 is coupled to the control electrode terminal' 14: of the next tube, through a blocking condenser 40, in'order to keep the anode potential of the tube 8 from the control electrode of the tube 10.` The control electrode of the tube 10 may be biased by an external source coupled to the lead 39, which may include a resistance, as shown. i

The output of the tube 10 istaken from the i anode terminal 18 to one side of the output circuit 48, the other side of which is connected to-the shield through a blocking con denser 50,' Tlie'output of the ainplifier is supplied to a utilization circuit through a r 7 i Screen' grids. It will also be noticed in Fig ure 2 that the' cathodes of the tubeslare conne'cted 'to'the shieldsiwith respect to radio frequency energy, 'therebyi conpleting 'the control electrode to 'cathode and 'the anodeto cathodecircuits' of the tubes; Cathode beat y o ing current, 'control' electrode" bias potential,

and anodepolari'zing potential are 'all ted through appropriate leads, connected between the blocking condensers and the appropriate electrodes, and preferably' provided With radio frequency chokes, as isindicated'in Figure2. lclaim: r "i In eombination, a ;shielding container including a vertical metallie partition divid ing it into a plur'ality of shielded compartmente, said Vertical partition having a cylindrical 'conductive 'shield extending there through' at a slant, said cylndrcal conductive' sheld bel g' ntegra lly ;connected to said yerioo ios

' i tical partition, an 'electron emission tube com' i r pri sing an 'anode`, a oathodacontrol elec trade, 'an 'anode' .terminal at one jend of the 

